Track and field is a sport in which athletes compete in running, jumping, and throwing events. In two events that combine running and jumping, the athletes jump over ten spaced apart hurdles in between the start and finish. A hurdle consists of a base, two uprights, and a horizontal gateboard. In the first hurdle event (commonly known as the high hurdles), athletes run about 100 yards and jump over relatively high hurdles. In the second hurdle event (commonly known as the low or intermediate hurdles), athletes run about 440 yards and jump over lower hurdles. The height of the hurdle in each of the events varies depending upon the age and sex of the athletes. For versatility and economy, most hurdles are adjustable in height.
A hurdle is designed to tip over if the athlete's foot or knee contacts it. In terms of physics, the hurdle tips when the torque applied to the gateboard is sufficient. Torque is defined as the force multiplied by the distance from the axis. The force at the gateboard required to tip the hurdle over is commonly known as its pull over weight. The pull over weight is a function of the height of the hurdle (the distance from the gateboard to the axis). Other things being equal, the pull over weight decreases as the height of the hurdle increases. Most hurdles contain added weights in the base to achieve the desired pull over weight. To maintain a constant pull over weight as the height of the hurdle changes, many modern hurdles incorporate a weight that moves in the base. As the height of the hurdle increases, the weight is moved further away from the uprights and, as the height of the hurdle decreases, the weight is moved toward the uprights. In some hurdles, the weight is moved manually. In other hurdles, the weight is connected mechanically to the gateboard so that it moves automatically as the gateboard is moved.
A hurdle with a movable weight connected to the gateboard is disclosed in Dellinger et al., U.S. Pat. No. 4,749,187, issued Jun. 7, 1988, which is incorporated by reference. The Dellinger et al. hurdle contains weights inside the base that are connected to the gateboard by a mechanical system consisting of cables, pulleys, and springs. The gateboard height and the positions of the weights are adjusted using a trigger mechanism located in the uprights. The spring and the trigger mechanism occasionally require service and, because of their locations, are difficult to repair.
Accordingly, a demand exists for an improved hurdle. In particular, a demand exists for a hurdle that contains a durable and easily used trigger mechanism that is not contained within the upright itself. A demand also exists for a hurdle with automatically movable weights connected to springs that are not contained within the base.